Prime Minister Pierre Trudeau's controversial plan to bring the Canadian constitution home from Britain ran into a significant snag yesterday when a British parlimentnary committee recommended that the plan be rejected.

Trudeau immediately denounced the committee for "interference," telling a news conference, "They have no right to decide what's good for Canada. It's as simple as that."

Trudeau professed not to be worried about the report, insisting that Prime Minister Margaret Thatcher had assured him she would push his proposals through the British Parliament once they were appraoved by the Canadian Parliament.

"If they're wise," Trudeau said of the British, "they'll get it through quickly and hold their nose while doing it and send it over."

Trudeau said he had warned Thatcher in June that any rejection of Canadian constitutional proposals would hurt Britian's image with other members of the Commonwealth.

"It would be funny for Britain to remain in the Commonwealth and to refuse to give complete and final independence to one of its former colonies if that is being requested," he said.

In its report, the British parliamentary committee on foreign and commonwealth affairs said that Britain should refuse to approve the constitutional proposals so long as they lacked substantial support from the governmentsof the Canadian provinces.

Trudeau has a majority of the Canadian House of Commons backing his plan. But he has won support for his proposals from the governments of only two provinces, Ontario and New Brunswick. A third, Saskatchewan, has not made a decision. The other seven provinces oppose the Trudeau plan. In fact, six of them have filed suit in Canadian courts, claiming that Trudeau has no legal right to enact his proposals without their approval.

The dispute results from a quirk in constitutional history that Trudeau is trying to set straight. The Canadian constitution is still a British law known as the British North American Act of 1867. When Canada became fully independent of Britain 1931, that law remained with the British Parliament. There seemed to be no point in transferring the law legally to Canada as a separate Canadian constitution until the federal government in Ottawa and the provincial governments culd agree on a formula for amending it. But, after a half-century of trying, Ottawa and the provinces have still failed to agree on one.

In October, Trudeau gave up trying and introduced a plan of his own: The British would be asked to expand the British North America Act by adding a charter of rights guaranteeing both civil liberties and language rights. A tentative amending formula, subject to approval by national referendum in Canada, would be added as well. The British Parliament would then legally transfer the constitution to Canada.

The proposals, as expected, provoked angry reactions from the governments of most of the provinces. While they insisted that they did not object to the principle of patriating the constitution, the premiers said they objected to the charter of rights, to the Trudeau amending formula and to his method of acting on his own.

Public opinion polls have indicated that a large majority of Canadians, although in favor of the goals, now oppose Trudeau's methods of trying to implement them. Some of Trudeau's own supporters in Quebec are angry about the failure of the charter of rights to require official bilingualism in Ontario, the province with the largest number of French speakers outside Quebec.

These problems, however, have evidently not shaken Trudeau's determination. Although his plan is opposed by both major parties in Quebec, Trudeau has described it as fulfillment of his pledge to Quebec residents in May that the federal government would change the constitution to their favor if they rejected separatism in the Quebec referendum.